Lifespan: Tenbun 23 (1554) to 12/12 of Tenshō 14 (1586)
Rank: bushō, daimyō
Title: Chief of the Imperial Guards, Assistant Captain of the Imperial Guards, Governor of Awa, Governor of Kawachi, Vice Minister of Popular Affairs
Clan: Miyoshi → Sogō
Father: Miyoshi Jikkyū
Adoptive Father: Sogō Kazumasa
Mother: Koshōshō (daughter of Okamoto Mokusai)
Siblings: Hosokawa Saneyuki (older brother of a different father) (?), Miyoshi Nagaharu, Masayasu, Chōsokabe Ukon Taifu (younger brother of a different father) (?)
Children: Senmatsumaru, Masahide, Bandō Yasunaga (Iga-no-kami)
Sogō Masayasu served as a bushō and daimyō during the Senogku and Azuchi-Momoyama periods.
In 1554, Masayasu was born as the second son of Miyoshi Jikkyū. Jikkyū was the younger brother of Miyoshi Nagayoshi.
Succession of the Sogō clan
In 1561, owing to the sudden death from illness of his father, Sogō Kazumasa, the lord of Sogō Castle in Sanuki, and, in 1563, the early death of Miyoshi Yoshioki, the head of the Miyoshi family and lineal heir of Miyoshi Nagayoshi, Kazumasa’s eldest son, Sogō Shigemasa (later known as Miyoshi Yoshitsugu), inherited the Miyoshi family. As a result, Masayasu was adopted by Kazumasa and inherited the Sogō family. Yoshitsugu’s younger brother, Sogō Masayuki, was an illegitimate child so could not inherit the Sogō family, and, instead, became Kazumasa’s chief retainer. However, Masayasu’s older brother, Miyoshi Nagaharu, was still young when he inherited the Awa-Miyoshi family so a former retainer of Miyoshi Jikkyū named Shinohara Nagafusa, along with Shinohara Jiton and Akazawa Sōden, supported the Miyoshi and Sogō families.
Masayasu first appears in records as the head of the Sogō family in 1568, and, in 1571, under the name of (Magorokurō) Masayasu.
Battles against Oda Nobunaga and separation from groups in Sanuki Province
Thereafter, Masayasu frequently joined in deployments by Shinohara Nagafusa. In the sixth month of 1566, Nagafusa obeyed Ashikaga Yoshihide, the Awa kubō, by leading forces from Shikoku to attack Miyoshi Yoshitsugu and Matsunaga Hisahide of Yamato. Masayasu and his older brother, Nagaharu, acted in concert with Nagafusa in the Battle at the Giant Buddha of Tōdai Temple, but, after Oda Nobunaga marched upon the capital of Kyōto to install Ashikaga Yoshiaki as the fifteenth shōgun of the Muromachi bakufu, Masayasu’s forces withdrew to Awa and Sanuki in Shikoku. In the seventh month of 1570, after the Miyoshi Group of Three and Miyoshi Yasunaga raised arms, triggering the Battle of Noda and Fukushima Castles, Masayasu coordinated with Nagafusa, landing forces in the Kinai for the second time, but, based on an imperial edict from Emperor Ōgimachi, he settled with Nobunaga and pulled back to Awa and Sanuki again.
In the third month of 1573, after a falling out with Miyoshi Nagaharu, Shinohara Nagafusa holed-up in Uezakura Castle. In the sixth month, upon orders of Nagaharu, Masayasu led a contingent of 7,000 soldiers including Mori Hida-no-kami and Izawa Ukon Taifu of Awa, the Kōzai clan of eastern Sanuki, and the Kagawa clan of western Sanuki, in addition to 3,000 supplemental forces from Kii Province (with an arsenal of 1,000 arquebuses) to attack Akazawa Sōden at Banzai Castle. Next, the forces launched an assault against Uezakura Castle and, on 7/15, killed Shinohara Nagafusa and Shinohara Nagashige at the Siege of Uezakura Castle.
Around this time, Masayasu may have started to collude with the Oda clan via Matsura Nobuteru of Izumi Province. In one account dated 4/19, Matsura Hizen-no-kami informed Nobunaga and Shibata Katsuie that he received a request from Sogō (no first name) to support an attack on Wakae Castle in Kawachi. An offer was then made so that if Sogō immediately attacked Wakae Castle, he would receive the fief of Miyoshi Yoshitsugu comprising one-half of Kawachi and Kakenokōri in Settsu. Moreover, even if the castle could not be captured on the first attempt, they would build an outlying base and if the attack eventually succeeded, he would receive one-half of Kawachi. However, among the Matsura clan serving as the intermediaries was a natural son of Sogō Kazumasa (Matsura Magohachirō, the lord of Kishiwada Castle). There is a possibility that the Sogō individual referred to in the letter was someone other than Masayasu. In any event, Miyoshi Nagaharu and Masayasu, as siblings, continued to oppose the Oda.
Thereafter, the kokujin of Sanuki began to show resistance toward the Miyoshi. After being ousted from Sanuki by the Miyoshi and Sogō during the period of approximately 1564 to 1577, the Kagawa clan received protection from the Mōri clan in Bitchū Province and continued to resist the Miyoshi during this period. In 1574, Kagawa Yukikage joined with the Kōzai clan of Katsuga Castle in Sanuki to oppose Nagaharu. Masayasu was warned in a letter signed by Kōzai Yoshikiyo and others of their intention to leave the Awa-Miyoshi family. The reasons given were the prior reallocation by Shinohara Nagafusa of the Ōuchi District from the Sangawa clan (a powerful kokujin in eastern Sanuki) in addition to the autocratic governance of Miyoshi Nagaharu. Nagaharu responded by dispatching troops, but other kokujin in Sanuki including the Ōnishi and the Nagao clans sympathized with the Kōzai clan while Chōsokabe Motochika of Tosa attacked Kaifu Castle in the southern portion of Awa so Nagaharu withdrew to Awa.
Meanwhile, in the Kinai, in the fourth month of 1575, Takaya Castle in Kawachi and Niibori Castle in Settsu fell, and Miyoshi Yasunaga surrendered to Nobunaga. At this time, Sogō Kazuyuki and Kōzai Naganobu (who had been holed-up in Niibori Castle) were killed during the Siege of Takaya Castle. As a result, the Miyoshi and Sogō clans completely lost their bases in the Kinai. Furthermore, after surrendering to Nobunaga, Yasunaga initiated subversion tactics among the kokujin in Awa and Sanuki on behalf of Nobunaga.
Around this time, the Miyoshi clan had completely lost control over the kokujin, or provincial landowners, of Sanuki. After separating from the Miyoshi, Kagawa Yukikage plotted with Kōzai Yoshikiyo, and then attacked and eliminated Kanakura Akitada, a retainer of the Miyoshi who served as a magistrate for the territory of the Nara clan in the Naka District. In 1576, the Kagawa and Kōzai clans both sent messengers to Oda Nobunaga and submitted to the Oda clan.
Battles against Chōsokabe Motochika of Tosa Province
In the third month of 1577, in Awa, Masayasu’s older brother, Miyoshi Nagaharu, was defeated by Hosokawa Saneyuki (Masayasu’s half-brother who was supported by Chōsokabe Motochika) and took his own life. In the seventh month, in Sanuki, members of the Kobayakawa clan landed in the Chūgoku Region, and aided Kagawa Minbu Taifu, the lord of Nishi-no-shō Castle, by attacking the Nagao and Hayuka castles at the Battle of Motoyoshi. Meanwhile, Masayasu was backed by the Miyoshi family and, in 1578, entered Shōzui Castle in Awa in a bid to restore the authority of the Miyoshi family in Awa. Thereafter, perhaps because he acted as the head of the Miyoshi family, his signature appears more frequently in historical records under the Miyoshi surname instead of the Sogō surname. The oldest known signature in the name of Miyoshi dates to 1574, indicating that he used the Miyoshi name while his older brother was still alive.
Later, Masayasu called for resistance to the Chōsokabe clan and succeeded in rallying a majority of the kokujin in Sanuki and Awa. Kagawa Yukikage, however, did not join the effort, and, instead, adopted Chōsokabe Chikakazu (the son of Chōsokabe Motochika) and joined the military of the Chōsokabe family.
In 1580, Oda Nobunaga did not approve of the subjugation of Shikoku by the Chōsokabe clan and pressured them to become his retainers, but Motochika refused these demands. This generated enmity between Nobunaga and Motochika. In the third month of 1581, with the support of Nobunaga, Miyoshi Yasunaga and Masayasu initiated counterattacks against Motochika. Yasunaga had his son, Yasutoshi, betray them, while Masayasu colluded with Hashiba Hideyoshi (later Toyotomi Hideyoshi) who was engaged in clashes with the Mōri clan in the western provinces, increasing the pressure on Motochika.
Around the fourth month of 1580, a senior retainer named Shinohara Ukyō-no-jō joined with Ichinomiya Narisuke to plan a rebellion, and, after Masayasu discovered the plot, he aimed to flee Sanuki. Masayasu began to collude with the Oda from around this time and, in the eleventh month, a group of rōnin, or wandering samurai, from Ōsaka who were ousted from the Ishiyama-Hongan Temple, joined with the Saika group from Kii Province and the Awaji group to occupy Shōzui Castle. After observing these developments, Masayasu separated from the Oda clan again and Shōzui Castle was returned to him. Owing to a subsequent deterioration in relations between the Oda and the Chōsokabe, Masayasu sided with Nobunaga.
Nevertheless, after the unexpected death of Nobunaga on 6/2 of Tenshō 10 (1582) in an event known as the Honnō Temple Incident, Masayasu lost his patron. In the eighth month, Kagawa Chikakazu attacked Fujio Castle where Kōzai Yoshikiyo was holed-up, and after Yoshikiyo surrendered to the Chōsokabe, that same month, the Kagawa and Kōzai clans attacked Sogō Castle defended by Sogō Masayuki, its chamberlain. The attacking forces, however, could not topple the castle.
Despite valiant efforts at the Battle of Nakatomigawa, Masayasu was defeated by Chōsokabe Motochika. He then proceeded to abandon Shōzui Castle in Awa and, in the ninth month, withdrew to Toramaru Castle in Sanuki. The Chōsokabe army converged with the Kagawa army and, with a combined force of 36,000 troops, assaulted Sogō Castle, but were unable to capture it in the First Siege of Sogō Castle. With the arrival of the winter season, the forces returned to Tosa. In the tenth month of the same year, Masayasu invaded Awa again and attacked Ibaragaoka Castle, compelling Hosokawa Saneyuki to kill himself. There is a theory that, because this overlapped with the timing of the invasion of Awa and Sanuki by the Chōsokabe army, Motochika was responsible for the killing of Saneyuki.
From the second month of 1583, he began to use the name Masayasu, but, from the eighth month, he used Miyoshi Yoshikata. The name Masayasu was intended as a means to reset the governor of Sanuki as the successor to Sogō Kazumasa, but after Hashiba Hideyoshi had his nephew (later known as Toyotomi Hidetsugu) become the adopted heir of Miyoshi Yasunaga and name him Miyoshi Nobuyoshi, this alarmed Masayasu. In addition to using the “Yoshi” character that had been used for generations by the main branch of the Miyoshi family, this expressed an intention to have Nobuyoshi inherit the main branch of the Miyoshi family rather than the Miyoshi or Sogō of Awa. Under another theory, based on his earlier use of the name Yoshikata, he adopted the name with a character from the name of Ashikaga Yoshiaki (the shōgun) based on consent from Yoshiaki for Masayasu to become the successor to the Miyoshi clan after Yoshiaki and the Mōri settled with the Miyoshi.
In the sixth month of 1584, when Sogō and Toramaru castles fell to Chōsokabe Motochika, Masayasu relied upon the support of Hashiba Hideyoshi (later known as Toyotomi Hideyoshi) of Ōsaka to escape. This is known as the Second Siege of Sogō Castle.
Conquest of Shikoku and Conquest of Kyūshū
In the sixth month of 1585, Masayasu cooperated with Toyotomi Hideyoshi in the Invasion of Shikoku, whereupon Hideyoshi granted Masayasu the former territory of the Sogō clan in the amount of 30,000 koku in Sanuki and restored his position with the status of a daimyō. This occurred in connection with the allocation of territory to daimyō and landowners from the eighth month of 1585 in the aftermath of the Invasion of Shikoku in an event known as the Allocation of Shikoku. Nevertheless, this was under the name of Sogō Magohachirō as a yoriki-daimyō or in the capacity of a security officer for the Sengoku clan, and denied the right to succeed to the main branch of the Miyoshi family or to possess territory in Awa.
In 1586, when Masayasu joined the Conquest of Kyūshū, during the Battle of Hetsugigawa, he became a victim of the reckless strategy of Sengoku Hidehisa to charge the enemy forces led by Shimazu Iehisa before the arrival of reinforcements and was killed in action. He was thirty-three years old.
At the time of the Battle of Hetsugigawa, Masayasu’s eldest son, Senmatsumaru, had not yet met Toyotomi Hideyoshi. Prior to dying, he told his retainers that if he were to die, to have his son meet Hideyoshi so the Sogō family would continue. After his death, however, his landholdings were seized.
Masayasu’s children included his eldest son, Sogō Senmatsumaru, and Sogō Masahide. Other documented names include Bandō Yasunaga, Buzen-no-kami Nagayasu, Utanokami Masayoshi, and Murata Kyūbei Masatsugu, but these have not been confirmed as his children.